The invention relates to a cast part. The invention also relates to a piece of equipment which comprises the cast part, to a method for producing the piece of equipment, and to a use of a tool for shaping the functional region of the cast part.
Such a cast part is disclosed in U.S. Pat. No. 4,134,036 A. The cast part disclosed in said patent can be produced as a bell-like cast part of aluminum or other high strength lightweight material. In many cases, with regard to its function, the cast part must be further developed after casting for use in a piece of equipment, by means of subsequent precision working at some time after the casting. The further development of its function may consist in a metallic functional region, by virtue of the subsequent precision working, being able to retain a further component of the piece of equipment. For example, in the cited patent the piece of equipment is an electrical machine in which a rotor is caused to rotate during operation as a result of current being injected into windings of a stator. The forces occurring in this case result in counterforces in the stator which in this case, as a further component of the electrical machine, is retained in its housing, i.e. in the cast part. For this purpose, the patent makes provision for e.g. longitudinal ribs on the inner side of the cast part, circular grooves and openings for fastening the housing to the remainder of a tool. The longitudinal ribs with their projections and ribs are intended to secure the stator in the housing, and to prevent a relative rotation between the housing and the stator. The grooves can be used to prevent any relative axial movement between the stator and the housing. Taking as a starting point the various possibilities for connecting a stator to the housing, the cited patent also describes retention of the stator in the housing by means of an interference fit. The stator here is additionally secured against twisting by means of a screw connection which extends into the stator from the outer side of the housing. This further functional development of the housing also requires the subsequent addition of a hole by means of metal-cutting work to the housing, i.e. the cast part. The securing of the stator against twisting in the housing is often necessary in order reliably to ensure the transfer of force and torque, both in the production process for positional retention and during the service life of the product under the influence of forces, torques and high thermal loads.
The document JP 2010-178589 A is concerned with improving the efficiency of a rotating electrical machine. The efficiency is effectively improved by virtue of an identical tensile stress acting on the laminated stator core. The internal diameter of the housing of the rotating electrical machine and the external diameter of the laminated stator core have the same value, and therefore the laminated stator core can be inserted into the housing. The laminated stator core has grooves in the axial direction along the surface of the laminated stator core. A rotating tool is used to rub on the housing, such that the material of the housing can flow into the grooves of the stator in plasticized form. The stator is thereby fastened to the housing at two or more points via its surface. If an aluminum alloy is used as a material for the housing, the rotating tool preferably has a rotary speed of 800 r/min and is preferably moved at a speed of 200 mm/min in an axial direction along the housing. The housing is made of a nonmagnetic material such as the aluminum alloy or can be made of an austenitic SUS material. The abbreviation. SUS signifies stainless steel in accordance with the Japanese industry standard JIS.
In the case of an austenitic structural constituent, the elongation at rupture A5 is approximately 40% to 50%. These values are defined e.g. in Wikipedia at the following link http://de.wikipedia.org/wiki/Austenit_(Gef%C3%BCgebestandteil).
The elongation at rupture is determined in a tensile test. The tensile test is a standard method of material testing for the purpose of determining the yield point, the tensile strength, the elongation at rupture and further material characteristic values. The tensile test is described e.g. at http://en.wikipedia.org/wiki/Tensile_testing. The elongation at rupture is determined on the basis of standardized test specimens.
In the case of rod-shaped test specimens having a circular cross section, the index 5 or 10 is generally used to define the elongation at rupture. This relates to the ratio k of a starting measured length L0 and a starting diameter d0 of the circular cross section. The elongation at rupture A5 is therefore determined in the case of a tensile test using a test specimen where k=5.
In the case of iron and steel sheet, the elongation at rupture is usually determined using a flat test specimen having a starting measured length L0 of 80 mm, and is defined as elongation at rupture A80mm or often simply as elongation at rupture A80.
In the case of non-ferrous metals, the elongation at rupture is usually determined using a flat test specimen having a starting measured length L0 of 50 mm, and is defined as elongation at rupture A50mm or often simply as elongation at rupture A50.
The elongation at rupture is normally determined at room temperature, e.g. 23° C.
The producers of cast materials or cast parts produced using these materials specify a minimum elongation at rupture for the material to be cast or the cast part, defining an elongation at rupture A which usually corresponds to the value A5, A10, A50mm or A80mm.
The document JP 2010-178598 A is concerned with improving the thermal conductivity between a laminated stator core and a metal housing, without the magnetic properties of the laminations degrading more in a combined part when the laminated stator core and the metal housing are connected. In order to achieve this, the laminated core is inserted into the cylindrical metal housing and the combined part is formed by means of friction stir welding of the laminated stator core and the metal housing. Since the connection is created by the kneading of the material during the friction stir welding and the plastic flow, melting of the magnetic laminations is not necessary. Since no great thermal stresses occur in the connection, the magnetic properties of the magnetic laminations are not significantly degraded. As a result of the material connection between metal housing and laminated stator core, the thermal conductivity is improved in comparison with a purely mechanical contact between metal housing and laminated stator core, and therefore the cooling of the dynamo-electrical machine is also improved. If the metal housing is produced from an alloy containing aluminum, the tool for the friction stir welding has a rotary speed of 800 r/min and is moved at a speed of 200 mm/min along the metallic housing. The tool is made of SKD61 (tool steel as per JIS, e.g. http://www.steel-grades.com/Steel-grades/Tool-steel-Hard-alloy/skd61.html), and comprises a cylindrical main part having a diameter of 20 mm and a cylindrical part having a diameter of 5 mm which projects 5 mm from the end thereof. The thickness of the housing is 6 mm. The penetration depth of the tool during the friction stir welding is 5.5 mm, wherein the housing has a thickness of 6 mm.